Memory Man info + question

[searoad]

resurrecting an old topic but back in the first post by ethanw, i checked this out:
Mod I found online:  http://germaniumsky.com/gsky/ideas2.html
and only tried the mod for doubling the delay time, super simple mod.  used a submini spdt switch and since my power slider switch broke i instead took the lead from the board and soldered directing to the power jack, removed the power switch and used the space for the submini switch to double delay time. i haven't tested out the mod with my normsl setup and volume but i'm pretty satisified by it... i think the added distortion noted in this mod i will not find to be much of a problem since i do mostly experimental and improv music...
thanks for the link, i'm abit of a newbie here so thats why i just found this...

Q: where do those two wires connect to ?
my DMM has a different layout from the photo's

[Gila_Crisis]

well if wanna an good DMM schem just look here:
http://www.experimentalistsanonymous.com/diy/Uploads/Deluxememoryman.pdf

!!!!

[Gila_Crisis]

do here anyone ever try changing the first 4558 with a TL072?

do this make a big difference? is it a valuable mod to do?

[DougH]

got a recent EH memory man (4xMN3008 w/relay switching) which I like, but any guitar seems to distort the input slightly. Just about any signal overloads the "overload" LED.  If you try to adjust the level to avoid this, the bypassed/unbypassed volumes don't match. Anyone know of a fix for this?

You know what, thanks. I think you just helped me make my decision about this:

http://www.diystompboxes.com/smfforum/index.php?topic=63488.0

~$300 and then there are basic headroom problems? No thanks... Sometimes EH is genuinely inspired, sometime it's just expensive junk.

I'll be looking at the Echo Park really closely now...

[rubix cube]

At the outputs of the first MN3007 in the schematic linked to above, there are two 2.4K resistors (R22 & R23) connected to C15.  At the other end of C15, there are two more resistors (R25 & R26).  However, in the older schematic that Stephen Giles posted (EH-7850?), that capacitor (actually two 2.2uF in series) is connected only to R25 (100K), and R26 is connected after R25.  Does anybody know why?

Also I've not seen the diode symbol in the Chorus/Vibrato section before.  I know it says 1N4001 in the schematic, but why the slightly different symbol?  Any info would be greatly appreciated. 

[ethanw]

More info:  The following text is from an old post on this forum that I couldn't find but it addresses the input issue, credit to the unknown poster.


"I redid a DMM a few months back.  First, the tone of the DMM is due to three main things - the memory chips, the input impedance, and the gain structure.  The 4558s were used because they are cheap, but they really just raise the noise floor.  You can replace all of them with TL072s without negatively affecting the tone, and the noise floor drops quite a bit and the dry sound (when active as your pedal is TB) has more clarity while the delays still have all the character you like.

So try TL072s in place of every 4558 - it's a cheap experiment and I think you'll agree with me.

Now, the stock input impedence is really low and there's a ton of potential gain on tap - much more than is needed, even using the DMM as a boost.  So replace the 100K resistor in the input with a 1M pot.  Here's the schematic:  http://www.freeinfosociety.com/electronics/schemview.php?id=381.

The stock gain structure has a 100K resistor before the opamp and a 1M pot in the feedback loop (this is the volume pot).  By changing the 100k resistor to a 1M pot, you can set it to the stock impedance and when the volume pot is on full, have 10x gain.  But you don't need 10x gain, and the stock impedance is really low and loads down the pickups in a passive guitar (particularly with single coils).  Put in the 1M pot and you can raise the input impedance and lower the overall gain available, finding a balance between a higher input impedance and still having enough gain on tap.  I liked the input pot set to about 500K, which still had enough gain (2:1 at max though I didn't use it on max) for a nice boost.  Really improved the sound and gave it more depth.

As to noise, the stock design is really terrible in terms of grounding.  All the jacks are connected to the chassis and the ground is just series from jack to jack to PCB to transformer, along with using the chassis as a ground path.  Replace all the jacks with nylon Switchcraft/Neutriks, or use shoulder washers on all jacks.  Run the grounds from the jacks and the PCB to the grounding point of the transformer.  Now there's only the one path to ground, and the chassis (which will be grounded only at the transformer as well) can shield but not serve as a ground path.  This should greatly reduce hum.

If you have any hum/noise at that point, the stock wire is terrible and runs all over the place.  Replace all the wires to/from the jacks and PCB with shielded wire."

[rubix cube]

That schematic is the one everyone says is wrong!

[jonathan perez]

whats wrong with it?

[rubix cube]

Isn't it the one that puretube refered to as the "never trust a schematic on the web" schematic?.  I can't find that thread right now, but here's the one with the schemo that Stephen posted, which does differ in the expandor section.  http://www.diystompboxes.com/smfforum/index.php?topic=61535.0.  I think the 1K resistor near the feedback pot is in a different place. 

[rubix cube]

This thread http://www.diystompboxes.com/smfforum/index.php?topic=56923.0

[jonathan perez]

aaah maaaan...

[rubix cube]

So the free information society one is supposedly wrong, but as far as I can see http://www.4shared.com/file/25305279/c5b4d23e/EHMM_ch_vib.html and http://www.experimentalistsanonymous.com/diy/Uploads/Deluxememoryman.pdf are right (?).  The latter looks like a reissue or summat, so there are a few different values, and the power supply is different.  There is also that difference that I noted in a post above, which I'm still confused about.

[big bustle]

I am very excited to try this out too. if it's just a simple act of putting a .1uF cap where do i sign up? what point are they on the circuit board. i have a later rev that doesnt macth the picture.

resurrecting an old topic but back in the first post by ethanw, i checked this out:
Mod I found online:  http://germaniumsky.com/gsky/ideas2.html
and only tried the mod for doubling the delay time, super simple mod.  used a submini spdt switch and since my power slider switch broke i instead took the lead from the board and soldered directing to the power jack, removed the power switch and used the space for the submini switch to double delay time. i haven't tested out the mod with my normsl setup and volume but i'm pretty satisified by it... i think the added distortion noted in this mod i will not find to be much of a problem since i do mostly experimental and improv music...
thanks for the link, i'm abit of a newbie here so thats why i just found this...

Q: where do those two wires connect to ?
my DMM has a different layout from the photo's

[g.]

SO ?

f it's just a simple act of putting a .1uF
what point are they on the circuit board

for extended delay ?

[big bustle]

yeah pretty much. i wired mine upo to a switch and it wroks pretty darn well. the bandwith is severly limited so it sounds pretty gnarly. it's totally qorth doing.

[g.]

can you tell me to wich components the added capacitor is connected ?
because i have a stereo memory man so  not the same board...

thanks !

[big bustle]

i cant recall

i googled around for a good hour and found pictures of someone else's build. theirs was a diff version than mine (both not stereo) but i was able to figure out what the 2 points were by looking at the chips.

[g.]

thanks !

i will looking for a schem...

[allmonochrome]

sorry to bump an older post, but has anybody figured out how to mod a deluxe mem. man so that it doesnt clip so much when hit with a hotter signal? it's what howard davis calls the "hot pickup mod."